Bosch Condens 7000 F - Test the Differential Pressure Switch for Continuity at Zero Pressure

Testing the differential pressure switch
55
Condens 7000 F – 6720871560 (2019/11)
 Pull off electrical connections at the differential pressure switch and
measure the resistance across the contacts (Fig. 68).
If the value measured is < 1 ohm (or signal tone, depending on
measuring device), the differential pressure switch is ok.
If no value, or a resistance of > 1 ohm, is displayed ( Fig. 69),
replace the differential pressure switch.
Fig. 68 Test the continuity of the differential pressure switch
(differential pressure switch ok).
Fig. 69 Test the continuity of the differential pressure switch
(differential pressure switch not ok).
 Following replacement, plug in (PWM signal) plug [1] at fan.
16.2 Test the differential pressure switch for continuity at
zero pressure
The differential pressure switch is open when the boiler is switched off.
There must be no negative pressure in the system when testing the
function of the differential pressure switch.
 Switch off the boiler at the control unit.
 Undo the union nut of the gas supply pipe at the flange on the air/gas
ratio control valve (Fig. 41, page 36).
 Pull off electrical connections at the differential pressure switch and
measure the resistance across the contacts (Fig. 70).
If no value, or a resistance of > 1 ohm, is displayed, the differential
pressure switch is ok.
If the value measured is < 1 ohm (or signal tone, depending on
measuring device; Fig. 71), the differential pressure switch is ok.
Fig. 70 Test the continuity of the differential pressure switch
(differential pressure switch ok).
Fig. 71 Measure the electrical resistance across the contacts of the
differential pressure switch (differential pressure switch not
ok)
 Following replacement, fit gas supply pipe to the air/gas ratio control
valve (Fig. 41, page 36).
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